Field of the Invention
The present invention relates to a method of manufacturing an electrostatic latent image developing toner used for image formation in electrophotographic image formation.
Description of the Related Art
As an electrostatic latent image developing toner (hereinafter, also simply referred to as “toner”) used in electrophotographic image formation, a toner that is more excellent in low-temperature fixability has been desired to achieve energy saving and an increase in speed of an image formation device. As such a toner, a toner that can be fixed at a low temperature due to a sharp melt property of a crystalline resin, by use of the crystalline resin together with an amorphous resin, as a binding resin.
As the crystalline resin, a crystalline polyester resin is typically known. Further, according to a toner using a urethane-modified crystalline polyester resin that is a combination of a polyester-based polymerized segment and a urethane-based polymerized segment, as the crystalline resin, a decrease in viscoelasticity in a high-temperature region at the time of heat fixation is suppressed, along with the sharp melt property of the crystalline resin. Therefore, occurrence of an off-set phenomenon is effectively suppressed.
However, when such a toner using the urethane-modified crystalline polyester resin is manufactured by a polymerization method, a problem like below is caused. That is, in the manufacturing of the toner by the polymerization method, fine particles of components of various toner particles are flocculated and fused in an aqueous medium, and the toner particles are obtained. However, for example, while a vinyl resin is typically used as the amorphous resin, the vinyl resin and the urethane-modified crystalline polyester resin are less likely compatible with each other. Therefore, fusion of the fine particles of the vinyl resin and the fine particles of the urethane-modified crystalline polyester resin at a fine particle interface is less likely to be facilitated. As a result, resultant toner particles become a toner with low mechanical strength.
To solve such a problem, a toner made of toner particles obtained such that the urethane-modified crystalline polyester resin particles are layered on a surface of a toner mother particles made of the amorphous resin has been proposed (for example, JP 2012-133161 A).
However, in the toner disclosed in JP 2012-133161 A, a crystalline resin component is exposed on a surface of the toner particles in the state of being layered on the surface of the toner mother particles. Therefore, there is a problem that the toner particles are more likely to cause heat fusion, due to an increase in temperature in the image forming device. Therefore, a heat-resistant storage property cannot be sufficiently obtained. Further, there are problems that the fixability is decreased due to compatibility between the crystalline resin and the amorphous resin in the toner mother particles at the time of heat fixing, and a document offset occurs.